2 exciting discoveries on Mars: recent water and new craters

[miriam_e]

Comparing photos from 1999 with those taken this year has turned up what looks very much like evidence of short-lived running water on Mars sometime over the last several years. The flows are not in the older images and they are the wrong color for sand-flows. They really look like liquid water seeped briefly out the side of a crater to flow down the slope before it evaporated or froze. Given the special importance of water for life, does that hold open the possibility that there is life in the Martian soil?

Also new are 20 impact craters over those 7 years. They range from about 2 meters (7 feet) across to about 148 meters (486 feet). That isn't a count for the whole planet though. The new images only cover about 30% of the surface, so extrapolating, this could mean something like 10 new impacts a year. This means that the smooth areas of Mars' surface are much younger than previously thought. But it is also a little scary. I wouldn't like to be nearby when something hits the ground to blast a crater the size of a several suburban houses.

Comments

[damien-wise.livejournal.com]

The flows are not in the older images and they are the wrong color for sand-flows.

Ta for answering that question. Most of the reading I've done this morning didn't tackle this issue, and I was worried it was a false-alarm. Water, ice and sand would all have different reflective indices, so it should be a relatively simple test.

But it is also a little scary. I wouldn't like to be nearby when something hits the ground to blast a crater the size of a several suburban houses.

Mirroring my thoughts, there. A Lunar base, or one on Mars, is a sitting target for this sort of disaster. Even a micro-meteorite (direct hit or near-miss) could devastate a structure, depressurise the building, etc. Not a pleasant thought. What we've seen so far are the results of only the larger and more obvious impacts...I think the overall frequency is much higher than indicated so far.
There's no obvious means of prevention, so how do you plan for it?
Also, what's the distribution?

[miriam-e.livejournal.com]

They're going to have to build underground anyway to protect against radiation storms from the sun. They just might want to dig a little further than previously expected. Of course over an area the size of Mars 10 per year is not very many. You'd have to be damn unlucky. And the thin atmosphere might mean the blast wouldn't have much of a shock wave... though the lighter gravity would mean ejecta would travel further. Ouch. ("And in the weather today, overnight CO₂ frosts at Pallas station, while at Aphrodite colony a light shower of rocks can be expected following this year's Perseid meteor shower, with major impacts predicted in mid-lattitudes for the weekend, and fine with temperatures in the high sub-zeros all next week." heheheh)

I don't know which 30% of of Mars the new photos covered. I should check online. I would suspect that frequency of impact would be higher closer to the equator, for the same reason that sun is hotter there. Polar lattitudes are angled away from the orbital plane (and presumably most of the orbiting objects) so would cop less impacts per unit area.

I suspect most impacts would hit in the morning too, when you are on the side of Mars sweeping stuff up as it races around in its orbit. I wonder if I'm right there, or if the disparity between meteor speed and planet speed is so great that time of day makes no difference.

I should have given the address:
http://www.nasa.gov/mission_pages/mars/news/mgs-20061206.html